Seal for electron discharge devices



June 22, 1937. A. KAUFFELDT SEAL FOR ELECTRON DISCHARGE DEVICES Filed Aug. 21, 1936 INVENTOR ALFoNs KAUFFELDT B y mW/d ATTORNEY Patented June 22, 1937 UNITED STATES PATENT oFFlCE v 21,084,913 SEAL Foa ELEcTnoN DISCHARGE DEVICES tion o! Germany Application August 21, 1936, Serial No. 97,130 In Germany November 19, 1935 '4 claims.

This invention relates to lead-in seals for electron discharge devices, particularly to seals for reducing electrical losses in insulating parts of the device between ,energized metallic members.

It has been found that considerable energy may be dissipated and destructive electrolytic action may take place in the glass press oi.' a discharge device, especially at high frequencies. In accordance with the invention, vlead-in conductors are passed through ceramic tubings which are passed through and sealed gas-tight in the press. The metal conductors are sealed vacuum-tight in the ceramic tubes in the known manner, preferably at the bottom end of the tubes and outside the press. It is also advantageous to enclose the conductorsin ceramic tubes when they are sealed into the envelope at points removed from the press. The ceramic tubes may conveniently be extended inwardly and employed to support electrodes within the envelope.

The novel features which are believed to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection 5 with the accompanying drawing in which the three figures are sectional views of electron dis'- charge devices embodying the invention.

The invention is applicable to many types of electron discharge devices, some of which will 0 be described in connection with the drawing. In

Figure 1 is shown a conventional formof press at I, and at 2 are electrode supporting posts which may be ceramic rods embedded at their lower ends in the press. According to the invention, lead-in conductors 4 are sealed vacuum tight in ceramic tubes 3 at the places 5. The ceramic tubes in turn are fused vacuum tight in the glass press at the places 6. Layers of ux or glass or the like may, if desired, be interposed between the metal conductors and the ceramic to facilitate sealing. In case of indirectly heated cathodes 'I it is advisable to pass these through the press with enclosing short ceramic tubing 8 separating the cathode carrier from the glass of the press. The ceramic tubing 8 may be soldered or sealed to the cathode carrier in any desired manner, leaving at ,the bottom sufficient room for the cathode lead-in il.

Figure 2 shows an electron discharge device in which the anode lead-in conductor is passed through the glass press in the usual manner, while the grid lead is brought in through a cer- 55 amic tube I0 at the top of envelope II, in order (cl. o-21.5)

to maintain the grid-anode capacity as low as possible.

A further modification represented in Figure 3 shows all lead-ins brought in through the press in ceramic tubes which extend inwardly to form electrode supporting means. A spacer plate I2, which may advantageously be of metal, is fitted to the notched ends I3 of the ceramic posts or extensions I4 of the tubes. The metal plate I2 may take the place oi the usual insulating spacers used with metal posts. Since the posts may be made of insulating material, and the spacers of metal, the holes in the spacers .can be accurately formed. To minimize inter-electrode capacities, it has been found desirable to bringthe lead-in conductor out through the side of the ceramic tube short of its inner end. In place of the metal plate I2, a plate of the usual insulating materials such as ceramic or mica may of course be employed. The metal plates as well as the insulating plates may be rigidly connected with the ceramic posts in accordancev with any of the known methods. Ceramic spacers have the advantage of small heat expansion. Other bridges or spacers may be provided at the lower end of the electrode system.

According to this invention the metal lead-in conductors may be provided with a more or less thick layer or coating of ceramic material which may be applied in a manner known in the manufacture of indirectly heated cathodes. To further reduce the detrimental influence of the different heat expansion coefficients of ceramic material and metal, the lead-in conductor may be formed as a thin metal wire Wound into a helix coated with ceramic material and sealed gastight in the envelope.

Alternatively the metallic conductors may also be produced by metallizing the inside of the ceramic tubings.

The characteristic features of this invention may advantageously be employed in the construction of gaseous discharge devices, in which it is often necessary to surround with an insulator an electrode supply line passing through. the discharge space, so as to prevent discharge thereat. An electrode assembly may be constructed that is extremely rigid and substantially free of changes in electrode spacing caused by temperature variations.

I claim:

1. An electron discharge device comprising an envelope with a reentrant stem and a. press, electrodes in said envelope, lead-in conductors connected to said electrodes and means for sealing said conductors m tight in said envelope comprising ceramic tubes extending through said envelope. said conductors extending through said tubes and sealed therein, and a. cathode sleeve v 5 embedded at one end in said press. a ceramic tube surrounding the embedded end of said cathode and sealed sas tight to the cathode and to the press.

2. An electron discharge device comprising an 10 envelope with a reentrant and a press. electrodes in said envelope, lead-in conductors connected to said electrodes and sealed gas tight in ceramic tubes, said tubes extending into the interior ot said envelope and mechanically secured to the electrodes, spacer means attached to the .ALFONS KAUFFELDT. 

